The present invention relates to electronic testing equipment and more particularly to a testing device used to determine the integrity of cables and wiring harnesses.
Known prior art devices used for testing cables and wiring harnesses include U.S. Pat. No. 4,689,551, U.S. Pat. No. 4,959,792, and U.S. Pat. No. 5,621,600. The testing of cables and wiring harnesses has historically been a trial and error procedure as described in the ""600 patent. If a wiring problem is detected, expert technicians would typically use an ohmmeter, a device used to measure resistance between two points on a wire, to detect a wire short. To determine which wire contains the short, the technicians must test each individual wire separately. Although the shorted wire would eventually be detected, the exact location of the short along the length of the wire would be unknown.
To locate the approximate location of the short, the prior art teaches the application of an audio range A.C. signal to the suspect wire or wire pair. An inductive type sensor, susceptible to magnetic fields created by an A.C. current is then used to determine the approximate location of the short. This is done by placing the sensor against the surface of the suspect wire or wire pair. The sensor provides an auditory tone whose volume depends on the strength of the magnetic field surrounding each particular wire. The user must physically place the sensor in close proximity with the wire itself to locate the fault. When the user no longer hears the auditory tone, the sensor is either too far from the wire or the wire has ceased conducting electric current. This lack of auditory tone alerts the user to the approximate location of the short.
The above mentioned inductive sensors have used both a high and low frequency audio range signal. The ""600 patent is an example of the use of a low frequency, low duty cycle signal applied directly to the suspect wire to determine the wire""s integrity.
The problems associated with this method are numerous. Using an aircraft as an example, the method above usually requires the removal of panels and any on-board computers or line replaceable units (LRUs) operatively associated with the cable. The time and expense involved in having a skilled operator execute this process for an aircraft having hundreds of miles of cable and wiring harnesses within its structure is considerable.
In addition to the inefficient use of time and resources, wear and tear upon the aircraft itself becomes an issue. A single wire malfunction may require the removal of suspect cables, wiring harnesses, on-board computers and the LRUs so that each wire may be tested. This requires removal of aircraft access panels which may then be subjected to damage as well as wear and tear from repeated openings and closings.
Patents ""792 and ""551 improved upon this method by using an electronic unit, capable of connection to both ends of a cable or wiring harness. The unit sending electronic signals down the length of each wire and measuring the results.
The concept of sending an electronic signal or pulse down a wire to test for shorts, opens, continuity, and resistance is known in the art. Further, the use of a microprocessor and memory device to electronically store the information gained from such a procedure is also known in the art.
Under the prior art, both ends of the cable or wiring harness being tested must be attached to the testing device. This results in extra expense, time consumption, and wear and tear. A single wiring harness may extend for hundreds of feet within the aircraft structure. Portions of the harness may extend in a multitude of directions throughout the aircraft""s structure. The user must locate both ends of each wire being tested, this will likely require removal of service panels and perhaps seating and cockpit instruments if the wire runs in close proximity to these items. The time and expense of locating and attaching the device to the wire is increased because both ends of each wire to be tested must be located and then made available for testing.
The present invention seeks to reduce repair time, expense, and wear and tear by allowing cables and wire harnesses to be tested and find the location of the problem without attachment of the testing device to both ends of each wire.
Accordingly, the present invention provides an automated, easy to use, windows based, portable, testing system for troubleshooting and investigating the integrity of test cables and wiring harnesses. The present invention uses a generic interface cable to connect the testing system to only one end of any cable or wiring harness to be tested. Once connected, the testing system runs a series of tests to determine the integrity of each wire within the cable or wiring harness. The data is then evaluated or compared to the data of a known good cable or wiring harness stored in a memory device or CD-ROM. The present invention displays which, if any, wires are faulty, a list of shorts or opens present between wires or between a wire and aircraft ground, and the exact distance to any detected fault.
The present invention places this information into an easy to understand visual display and also provides repair assistance information including a picture of the aircraft or other structure containing wiring. The picture displays each wire at issue and the exact position of the wire fault. The present invention further determines the resistance of a particular wire with respect to other wires or with respect to aircraft ground. The system also performs a connectivity test to determine whether a cable or wiring harness or individual wire under test is connected to a component. The present invention also provides a self-test feature which allows the internal circuitry of the testing unit itself to be checked to ensure testing reliability.